The present invention relates generally to flow meters for measuring the flow amount of a fluid passing through a passage.
Various devices and systems have been devised theretofore to measure the flow amount of a fluid passing through a passage. One known arrangement is that an impeller is provided to be rotatable about the axis of a fluid flow and the flow amount measurement is made by detection of the turning number of a ball made of a magnetic material and provided in operative relation to the impeller. Although satisfactory for measuring flow with relatively large amount (over about 3 l/min.), such an arrangement is disadvantageous in accuracy of detection of flow with a relatively small amount (about 0.3 to 2 l/min.) and in size-reduction of the apparatus and further in that the detection of the turning number is unstable because of deflection of the ball in the directions of the axis of the fluid flow. These disadvantages result in difficulty being encountered to employ it for systems necessary to stably measure flow with a relatively small amount and for small-sized apparatus such as a sanitary cleaner to be inserted into a human body.